Heat exchanger



10, 1954 P. E. J. M. MALDAGUE HEAT EXCHANGER 4 Sheets-Sheet 1 Filed Oct.14, 1949 a Q w lllll lllll llwlllll 0 6 P HWHW m m H 1+ iv i ||l||||L|:||:||.. 11| 1r l- 0, 1954 P. E. J. M. MALDAGUE 7 2,686,044

HEAT EXCHANGER Filed Oct. 14, 1949 4 Sheets-Sheet 2 Aug. 10, 1954 P. E.J. M. MALDAGUE HEAT EXCHANGER 4 Sheets-Sheet 3 Filed Oct. 14, 1949 x...axzjeu 4 Sheets-Sheet 4 Hm I D M I 3 9 wwwwmw M 1954 P. E. J. M.MALDAGUE HEAT EXCHANGER Filed Oct. 14, 1949 Patented Aug. 10, 1954 HEATEXCHANGER Pierre Edmond Jules Marie Maldague, Seraing, Belgium, assignorto Societe Anonyme John Cockerill, Seraing, Belgium, a Belgian companyApplication-October 14, 1949, Serial No. 121,347

Claims priority, application Belgium October 16, 1948 in heat exchangerswith a nest of tubes the transmission of heatis effected between astream of fluid circulating through the interior of the tubes andanother stream of fluid circulating over the outside ofthe tubes. Thetubes forming the nestof tubes are secured in a fluid-tight manner intubular plates by means of swaging or ramming. In many applications itis indispensable that the tubes forming the nest of tubes may bereplaced individually in the case of deterioration;

the easy replacement of each tube individually is only possible when theaxis of the tubes is at constant curvature and at constant torsion, thatis to say, that from a technical point of view this axis is eitherstraight or curved along an arc of a circle.

In these exchangers, it is also desirable for the coefficient of thermaltransmission to be as high as possible so that it is possible to reducethe surface of heat transmission and consequently, the

cost of the apparatus. It is also necessary to take care that thestreams of fiuid passing through the apparatus are subjected to theminimum possible loss in load so that the mechanical power dissipated inthe apparatus is at a minimum. Finally it is desirable thatirregularities in temperature of the various parts of the apparatus donot cause the appearance of considerable stresses in the metal.

Up to the present time it has not yet been possible to obtainsimultaneouslyall the desiderata referred to above.

The present invention has for its principal object to provide a methodof construction of heat exchangers with a nest of tubes whichsimultaneously produces a satisfactory transmission of heat, a low lossof load in connection with each of the streams of fluid, low stressesdue to thermal planatory description set out hereinafter With' referenceto the accompanying drawings of some forms of construction of heatexchangers according to the invention.

Figures 1 and 2 are diagrammatic illustrations of tube contours andderivation thereof. Figure 3 1 Claim. (01. 257-224) 2 is a diagrammaticlongitudinal section illustrating tube layer disposition. Figure 4diagrammatically illustrates the arrangement of tubes in a layer.Figures 5, 6 and '7 diagrammatically illustrate an arrangement of tubeshaving a noncylindrical central portion. Figure 8 is a side elevation ofa heat exchanger. Figure 9 is a section taken along the line A-A ofFigure 8 and Figure 10 is a section taken along the line B-B of Figure8. V

Fig. 1 shows diagrammatically the outer contour of the nest of tubes ofa heat'exchanger according to the present invention.

The surface, casing of the nest of tubes, is a cylindrical surface ofrevolution about the axis a, the generating line of this cylindricalsurface being the line b. The volume in which is contained eral shapeconverging from-the section 3 to the section 4.

Fig. 2 shows a straight cylinderidentical with that in Fig. l,included'bet-ween the sections 2 and 3, this cylinder being extended inFig. 2 up to the sections and 4 in Fig. 1. The section iii is the middlesection of Figs. 1 and 2.

The straight line segment 0 in-Fig. 2 represents the line, in the planeof'the drawing, of a semi plane at right angles'to the plane of thedrawing passing through the points'5'and t and through the point ofintersection of the axis a in the section It, the intersection of thissemi-plane with the'cylinder of Fig. 2 being the semi-ellipse shown inFig. 2 after folding in the plane of'the drawing. The points '1', 8 and9 of the folded semi-ellipse d are folds at the respective piercingpointslt and 9 of the semi-ellipse inthe respective sections 2, ill and3. The-curve e in Fig. Z-indicates an arc of a circle of correct size,defined by the three points if, 8' and 9, and limited-at H and E2. Thesegment 0 of Fig. 2 also representsthe projection, in the plane of thedrawing, of the arc of circle e brought into the secant plane of the Isection thus obtained from the generating line b,

comprised between the sections 2 and 3, being generally approximatelyand not rigorously a straight line. From a sectional point of view, thislatter approximation is without practical importance, as the differencebetween a straight cylinder and the actual cylinder comprised betweenthe sections 2 and 3, is comprised within the tolerance of manufacture.When a predetermined tolerance is adopted for the dimensions of a truecylinder between the sections 2 and 3, it is possible to take thistolerance into consideration in drawing the arc of circle e, so thatthis is not defined rigorously by the points I, 8', and 9 but maydeviate therefrom within limits defined by the admitted tolerances.

The method of generation of the surface shown in Fig. 1, by the rotationof an arc of circle about an axis, constitutes the principle ofconstruction of heat exchangers with a nest of tubes according to theinvention. In apparatus 'according to the invention the various layersof tubes are obtained in such a manner that all the axes of the tubesconstituting a layer are contained within a cylindrical surface obtainedin the manner shown in Figs. 1 and 2, the various layers having the sameaxis a and the same median plane i9.

Fig. 3 shows a section, through an axial plane, of the variouscylindrical surfaces containing the layers of tubes constituting thenest of tubes according to the invention, the lines 1 indicating thetrack of these surfaces in the plane of the drawing. The sections l, 2,3 and 4 of Fig. 3 are those defined in Figs. 1 and 2.

Fig. 4 shows the arrangement of the tubes in a layer, according to theinvention, the tubes being curved along an arc of a circle e defined inFig. 2 and the terminal sections I and 4 being those defined in Figs. 1and 2.

The method of construction of the nests of tubes according to theinvention, may adapt itself to apparatus of very diverse dimensions, byreason of the freedom of selection which exists for the respectivepositionings of the sections i, 2, 3, ti and i9 and of the points 5 and6, defined in Fig. 2. In particular, it is possible to obtain a nest oftubes in which the straight cylindrical portion comprised between thesections 2 and 3 is of zero value.

This last particular case may be obtained in the following two ways.

In the first way, the tubes having only a slight or zero curvature andeach layer of tubes then has the shape of a hyperboloid of revolution,as shown in Fig. 6 in which the lines it represent the axes of the tubesforming a layer. In the second way, all the tubes forming the layer havea determined curvature and their axes are located in axial planes of thenest. Fig. 5 shows aview or" such a layer of tubes, the lines gindicating the axes of the tubes forming this layer.

Other constructions of nests of tubes, according to the invention, canbe obtained by juxtaposition of the partial elements, taken from theconstructions above described. For example, it is possible to arrangethe curved tubes in the arc of a circle in such a manner that their axesg are contained in one plane, as shown in Fig. 5, and a number of planesof tubes of this type may be juxtaposed in such a manner as to obtain anest of tubes of arbitrary section varying arbitrarily.

The nest of tubes, according to the invention, obtained as abovedescribed, are secured in a known manner by swaging or by ramming intubular plates. The tubular plates are more frequently plane but theymay be arched.

In the case of heat exchangers with a nest of tubes which are to resista high pressure, the nests of tubes, according to the invention, lendthemselves particularly well to the construction of arched tube sheets,as the surface of these arched tube sheets may be substantiallyrectangular to the axes of the tubes, as indicated diagrammatically inFig. '7, in which the lines 2' indicate the axes of the tubes and aindicates an arched tube sheet.

Fig. 8 shows, descriptively and not in any way in a limiting sense, animproved heat exchanger according to the invention. The lines I and thetubular plates define the position or" the nest of tubes according tothe invention, of which a tube 70 is shown. The casing 11. consists of astraight central cylindrical section and two end truncated sections intowhich the admission and outflow of fiuid in circulation to the outsideof the tubes takes place through the tubular members p and q. The fluidcirculating in the interior of the tubes is guided by the tubularmembers r and s bolted in a known manner to the plane tubular plates m.The axis a of the apparatus is also the axis of the nest of tubesaccording to the invention. The detail of the arrangement of the tubesin the respective sections A-A and BB of Fig. 8 shows that the crosssectional passage of fluid outside the tubes of the nest is appreciablygreater in the inlet and outlet sections of this fluid than in thecentral cylindrical section.

What I claim is:

A heat exchanger comprising in combination a pair of end plates, aseries of tubes extending in longitudinally adjacent relationship andmounted between said end plates to form a bundle body having a generallycylindrical central portion of substantial length and divergent endportions, the center line of each of said tubes constituting an arc of acircle throughout its length facing concavely inwardly toward thecentral longitudinal axis of said bundle body, said tube center linesbeing each disposed in planes forming equal acute angles with saidcentral axis.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,125,758 Stack Jan. 19, 1915 1,655,086 Blending Jan. 3, 19281,869,973 Lucke Aug. 2, 1932 2,346,822 Clancy Apr. 18, 1944 FOREIGNPATENTS Number Country Date 1,136 Australia Dec. 30, 1931 of 1931 3,792Great Britain Dec. 14, 1872 of 1872 112,222 Great Britain Jan. 3, 1918563,894 Germany Nov. 11, 1932 570,115 Great Britain June 22, 1945

